134 MAN AND THE LOWER ANIMALS. n 



tween man and the apes, Nature has provided us, 

 in the latter animals, with an almost complete 

 series of gradations from brains little higher than 

 that of a Rodent, to brains little lower than that 

 of Man. And it is a remarkable circumstance, that 

 though so far as our present knowledge extends, 

 there is one true structural break in the series of 

 forms of Simian brains, this hiatus does not lie 

 between Man and the man-like apes, but between 

 the lower and the lowest Simians; or, in other 

 words, between the old and new world apes and 

 monkeys, and the Lemurs. Every Lemur which 

 has yet been examined, in fact, has its cerebellum 

 partially visible from above, and its posterior lobe, 

 with the contained posterior cornu and hippo- 

 campus minor, more or less rudimentary. Every 

 Marmoset, American monkey, old world monkey, 

 Baboon, or Man-like ape, on the contrary, has its 

 cerebellum entirely hidden, posteriorly, by the 

 cerebral lobes, and possesses a large posterior 

 cornu, with a well-developed hippocampus minor. 



In many of these creatures, such as the Saimiri 

 (Chrysothrix), the cerebral lobes overlap and ex- 

 tend much further behind the cerebellum, in pro- 

 portion, than they do in man (Fig. 17) — and it 

 is quite certain that, in all, the cerebellum is com- 

 pletely covered behind, by well developed posterior 

 lobes. The fact can be verified by every one who 

 possesses the skull of any old or new world mon- 

 key. For, inasmuch as the brain in all mammals 



